Effects of Planting Density on the Physiological Characteristics and Yield of Winter Wheat under Walnut-Wheat Intercropping System

【Objective】 To explore the effects of planting density on photosynthetic characteristics of flag leaves andyieldof winter wheat in nuclear wheat intercropping model. 【Method】 Using Xindong 40 as the test material, from 2016-2017, planting densities of 4.5 million plants/ha (M₁), 5.25 million plants/ha (M₂), 6 million plants/ha(M₃), 6.75 million plants/ha(M₄) and 7.5 million plants/ha(M₅) were set in nuclear wheat intercropping fields. The responses of net photosynthetic rate (P_n), Transpiration rate (T_r), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), yield and yield components of winter wheat in different canopy areas of walnut to planting density were studied. 【Result】 The results showed that as the density increased, the net photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (G_s)and yield of winter wheat in the sub-canopy showed different degrees. P_n,T_r,G_s of wheat’s flag leaves and yield in the far-crown region showed a “rising first and then decreasing” change pattern, and each index basically reached the maximum during M₂ treatment, and P_n,T_r,G_s, of winter wheat’s flag leaves under different densities were lower than those in the corresponding canopy regions. In terms of grain yield, the highest treatment under M₁ (4.5 million plants/hm ²) in the crown area was 3,212.19 kg/hm ², and the highest treatment in M₂ (5.25 million plants/hm ²) in the far crown area was 3 911.12 kg/hm ². 【Conclusion】 To sum up, under nuclear wheat intercropping mode, winter wheat should be sparsely planted in the canopy area, planting density should be controlled within 4.5 million plants/hm ², and suitable planting density for winter wheat in the far crown area is 5.25 million plants/hm ².